Plants in cold climates have evolved to have lower stature, tougher leaves, and biochemical properties preventing the formation of ice crystals. Even though lineages of such cold-adapted vascular plants from mid-latitude mountain regions—such as the Himalayas and Rocky Mountains—are also found in Arctic regions, species richness is lower in the Arctic.
This study used GBIF-mediated occurrences of more than 5,000 species occupying cold climates to generate stacked distribution maps confirming this observation. The authors used a model to derive environmental predictors of cold-adapted richness patterns, showing that richness is strongly associated with ecoregions.
Mapping the cold climate of the entire Northern Hemisphere from 60 million years ago to now, the authors showed that while cold regions—with temperatures below 0°C—started appearing in mid-latitude regions with the Himalayan uplift about 42 million years ago, cooling in the Arctic did not start until about 10 million years later, and the region as a whole was not comparably cold until much later.
The overall results indicate that early cooling of alpine regions allowed for evolution and diversification of cold-adapted vascular plants, followed much later by colonization of the Arctic.